A hot-air furnace for a grain dryer

Abstract

The present application belongs to the technical field of grain drying equipment, and particularly relates to a hot blast furnace of a grain dryer, comprising a furnace body, a burner and a heat exchange pipe being arranged in the furnace body in a left-right distribution, a flue gas discharge port of the burner being communicated with the heat exchange pipe, an outlet end of the heat exchange pipe being connected to a top induced draft fan, the top induced draft fan guiding the flue gas to flow through each heat exchange pipe and then to be discharged, a first air inlet being arranged on a side of the furnace body away from the burner, a second air inlet being arranged on the furnace body at a bottom of the burner, an air heating flow channel being formed between an outer wall of the heat exchange pipe and an internal space of the furnace body, a hot blast outlet being arranged on a top of the furnace body, air in the air heating flow channel being discharged under the action of negative pressure at the hot blast outlet, and a flue gas purification device being further arranged on the flue gas flow channel. The hot blast furnace of the grain dryer provided by the present application has the advantages of simple layout, low energy consumption, high heat exchange efficiency and environmental friendliness.

Description

Technical Field

[0001] This invention belongs to the technical field of grain drying equipment, specifically relating to a hot air furnace for a grain dryer. Background Technology

[0002] Grain dryers are essential equipment for post-harvest grain processing, with the hot air furnace being its core component, providing a heat source. The hot air furnace generates high-temperature flue gas through a burner, uses the heat from the flue gas to heat air, and then sends the hot air into the dryer to dry the grain.

[0003] In order to guide the high-temperature flue gas through various heat exchange tubes for heat exchange, traditional hot blast stoves typically require multiple blowers installed in different sections of the flue gas duct to drive the flue gas flow through a multi-stage pushing method. This multi-blower arrangement has drawbacks such as a large number of devices, high energy consumption, difficulty in coordinating and controlling the blowers, and high maintenance costs.

[0004] With increasingly stringent environmental protection requirements, flue gas emitted from hot blast stoves needs to undergo multiple purification processes, including desulfurization, denitrification, and dust removal. However, the composition and emission conditions of the flue gas from hot blast stoves are not constant during actual operation. Combustion temperature, excess air coefficient, and flue gas flow rate all change during startup, low-load operation, or when fuel quality fluctuates, leading to significant differences in the concentration of nitrogen oxides (NOx) and particulate matter in the flue gas. Current technology lacks an integrated purification device capable of flexibly switching purification modes according to the actual operating conditions of the hot blast stove. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a hot air furnace for a grain dryer, which has the advantages of simple layout, low energy consumption, high heat exchange efficiency, and environmental friendliness.

[0006] To solve the above-mentioned technical problems, the objective of this invention is achieved through the following technical solution: A hot air furnace for a grain dryer includes a furnace body. Burners and heat exchange tubes are arranged on both sides inside the furnace body cavity. The flue gas discharge port of the burner is connected to the heat exchange tubes. The outlet end of the heat exchange tubes is connected to a top induced draft fan. The top induced draft fan guides the flue gas flow through each heat exchange tube and then discharges it. A first air inlet is provided on the side of the furnace body away from the burner. A second air inlet is provided on the furnace body at the bottom of the burner. An air heating channel is formed between the outer wall of the heat exchange tubes and the internal space of the furnace body. A hot air outlet is provided at the top of the furnace body. The air in the air heating channel flows out at the hot air outlet under negative pressure. The flue gas duct is also equipped with a flue gas purification device, including: The first purification zone is located on one side of the inner cavity of the flue gas purification device, and its bottom is connected to the upstream side of the flue gas flow channel. A first ammonia water spray pipe and a static mixer are arranged in the first purification zone along the air flow direction. The second purification zone is located on the other side of the inner cavity of the flue gas purification device, and its bottom is connected to the downstream side of the flue gas flow channel. A catalytic reactor is installed in the second purification zone, and the shell of the catalytic reactor is sealed to the flue gas outlet of the second purification zone. A movable partition is disposed between the first purification zone and the second purification zone. The movable partition can be switched between an upper position and a lower position. When the movable partition is in the upper position, the bottoms of the first purification zone and the second purification zone are directly connected. When the movable partition is in the lower position, the bottoms of the first purification zone and the second purification zone are separated, while the tops are connected.

[0007] As a further improvement of the present invention, the heat exchange tubes are arranged as interconnected multi-stage heat exchange components, each stage of the heat exchange component is provided with an upper flue gas chamber and a lower flue gas chamber, and the upper or lower flue gas chambers of adjacent heat exchange components are connected to form a series flue gas flow channel, and the top induced draft fan is connected to the upper flue gas chamber of the last stage heat exchange component.

[0008] As a further improvement of the present invention, the flue gas purification device is externally placed on the top of the furnace body, and its first purification zone and second purification zone are respectively connected to the upper flue gas chamber of the two adjacent heat exchange components.

[0009] As a further improvement of the present invention, the heat exchange tubes in the multi-stage heat exchange assembly include at least two different diameter specifications, and the diameter of the heat exchange tubes in the upstream heat exchange assembly is not less than the diameter of the heat exchange tubes in the downstream heat exchange assembly; for example, three or more stages of heat exchange assembly can be set up, the first stage heat exchange assembly uses large diameter heat exchange tubes, the second stage heat exchange assembly uses medium diameter heat exchange tubes, and the third stage and subsequent heat exchange assemblies all use small diameter heat exchange tubes.

[0010] As a further improvement of the present invention, an ammonia water supply device is provided on one side of the furnace body. The delivery end of the ammonia water supply device is connected to a first ammonia water spray pipe and a second ammonia water spray pipe. The second ammonia water spray pipe is connected to the burner shell and sprays water toward its inner cavity.

[0011] As a further improvement of the present invention, the static mixer includes an array of static mixing fixing plates, and a plurality of staggered static mixing blades are obliquely arranged on the static mixing fixing plates; the staggered distribution can be a staggered distribution of static mixing blades between different transverse static mixing fixing plates, a staggered distribution of static mixing blades between different longitudinal static mixing fixing plates, or a staggered distribution of static mixing blades between transverse static mixing fixing plates and longitudinal static mixing fixing plates.

[0012] As a further improvement of the present invention, the second air inlet is opened on the bottom plate of the furnace and includes a number of through holes evenly spaced in the circumferential direction. The second air inlet is arranged around the outer periphery of the burner shell. The through holes constituting the second air inlet are preferably arc-shaped holes.

[0013] As a further improvement of the present invention, a power unit is mounted on the top of the flue gas purification device, the power unit being connected to the movable partition and driving its lifting and lowering; the power unit is preferably an electric push rod; a limit switch for controlling the position of the push rod is provided on one side of the electric push rod.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention provides a hot air furnace for a grain dryer. By setting a single induced draft fan at the top of the furnace body, the negative pressure generated by the single induced draft fan can drive the high-temperature flue gas in all heat exchange tubes to flow synchronously. This replaces the traditional solution that requires setting multiple blowers in different pipe sections, which greatly reduces the number of equipment, reduces power consumption, and simplifies control logic and maintenance.

[0015] 2. This invention features a first air inlet on the side of the furnace body furthest from the burner, and a second air inlet at the bottom of the burner. Air introduced through the first air inlet flows over the outer wall of the heat exchange tubes, absorbing heat from the high-temperature flue gas through the inlet. Air introduced through the second air inlet flows around the burner shell, absorbing radiant heat from the burner and heat from the shell. The two streams of hot air converge at the top of the furnace body and are then discharged through the hot air outlet into the dryer. This dual-inlet layout achieves dual recovery of high-temperature flue gas and radiant heat from the burner, significantly improving the thermal energy utilization rate of the hot blast furnace.

[0016] 3. This invention provides a dual-mode flue gas purification structure: In deep purification mode, the first and second purification zones are separated at the bottom but connected at the top. Flue gas enters from the bottom of the first purification zone, flows upward through an ammonia spray pipe and a static mixer, and after being sprayed to absorb and remove acidic gases (SO2, HCl, etc.) and dust particles, it flows downward through a catalytic reactor for catalytic reduction to remove nitrogen oxides (NOx) before being discharged. In this mode, the flue gas undergoes wet purification and dry catalytic purification sequentially, achieving deep desulfurization, dust removal, and denitrification, suitable for high pollution loads or conditions with strict emission standards. In energy-saving purification mode, the first and second purification zones are directly connected at the bottom. After entering from the bottom of the first purification zone, the flue gas bypasses the spray and mixing areas and directly enters the second purification zone, only being treated by the catalytic reactor before being discharged. This mode is suitable for low pollution loads or conditions sensitive to flue gas moisture content, avoiding the consumption of spray liquid and the decrease in catalyst activity due to moisture contact, extending catalyst lifespan, and reducing operating costs. Attached Figure Description

[0017] Figure 1 This is a perspective view of the present invention; Figure 2 This is an internal perspective view of the present invention; Figure 3 This is an internal perspective view of the present invention (from another angle); Figure 4 This is an internal perspective view of the flue gas purification device of the present invention; Reference numerals: 1. Furnace body; 2. Burner; 3. Heat exchanger tube; 4. Top induced draft fan; 5. First air inlet; 6. Second air inlet; 7. Hot air outlet; 8. Flue gas purification device; 9. First purification zone; 10. First ammonia spray pipe; 11. Static mixer; 12. Second purification zone; 13. Catalytic reactor; 14. Movable baffle; 15. Upper flue gas chamber; 16. Lower flue gas chamber; 17. Ammonia supply device; 18. Second ammonia spray pipe; 19. Static mixing fixing plate; 20. Static mixing blades; 21. Furnace bottom plate; 22. Power unit. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. See also: Figure 1-4 : This embodiment provides a hot air furnace for a grain dryer, including a furnace body 1. Burners 2 and heat exchange tubes 3 are arranged horizontally within the inner cavity of the furnace body 1. The burners 2 are used to burn fuel to generate high-temperature flue gas, and the heat exchange tubes 3 are used to achieve heat exchange between the high-temperature flue gas and air.

[0019] The flue gas exhaust port of burner 2 is connected to the flue gas inlet end of heat exchange tube 3. The heat exchange tubes 3 are arranged as a multi-stage, sequentially connected heat exchange assembly. Each stage of the heat exchange assembly includes several parallel heat exchange tubes 3, and each stage is equipped with an upper flue gas chamber 15 and a lower flue gas chamber 16. The flue gas chambers of adjacent heat exchange assemblies are connected in a shared manner: the upper flue gas chamber 15 of the previous stage is shared with the upper flue gas chamber 15 of the next stage, the lower flue gas chamber 16 of the previous stage is shared with the lower flue gas chamber 16 of the next stage, and so on, forming a serpentine series flue gas flow path between each stage of the heat exchange assemblies. The top induced draft fan 4 is connected to the upper flue gas chamber 15 of the last stage of the heat exchange assembly to generate negative pressure, guiding the high-temperature flue gas flow through each heat exchange tube 3 before discharge.

[0020] A first air inlet 5 is located on the side of the furnace body 1 away from the burner 2, and a second air inlet 6 is located on the furnace body 1 at the bottom of the burner 2. An air heating channel is formed between the outer wall of the heat exchange tubes 3 and the internal space of the furnace body 1. The air entering through the first air inlet 5 flows laterally across the outer wall of each heat exchange tube 3, absorbing the heat of the high-temperature flue gas through the partition wall, forming a stream of hot air; the air entering through the second air inlet 6 flows upward around the outer periphery of the burner 2 shell, absorbing the radiant heat of the burner 2 shell, forming another stream of hot air. The two streams of hot air converge at the top of the furnace body 1 and are discharged through the hot air outlet 7. The hot air outlet 7 is used to connect to the hot air inlet of the dryer, and under the negative pressure of the induced draft device on the dryer side, the hot air in the air heating channel continuously flows out.

[0021] Preferably, the second air inlet 6 is located on the furnace bottom plate 21 and includes several circumferentially evenly spaced through holes. The through holes surround the outer periphery of the burner 2 shell, forming an annular air intake area. The through holes are preferably arc-shaped.

[0022] A flue gas purification device 8 is also installed on the flue gas flow channel. In this embodiment, the flue gas purification device 8 is externally located on the top of the furnace body 1, and its first purification zone 9 and second purification zone 12 are respectively connected to the upper flue gas chamber 15 of the two adjacent heat exchange components. Specifically, the bottom of the first purification zone 9 is connected to the upper flue gas chamber 15 of the (N-1)th stage heat exchange component, and the bottom of the second purification zone 12 is connected to the upper flue gas chamber 15 of the Nth stage heat exchange component, so that the flue gas purification device 8 is integrated on the flue gas flow channel between the two adjacent heat exchange components.

[0023] The flue gas purification device 8 includes a first purification zone 9, a second purification zone 12, and a movable partition 14. The first purification zone 9 is located on the right side of the inner cavity of the flue gas purification device 8, with its bottom connected to the upstream side of the flue gas flow channel. A first ammonia water spray pipe 10 and a static mixer 11 are arranged along the airflow direction within the first purification zone 9. The first ammonia water spray pipe 10 sprays atomized ammonia water into the flue gas, allowing the ammonia water to contact and capture acidic gases and dust particles in the flue gas. The static mixer 11 forces the flue gas and ammonia water droplets together, enhancing the gas-liquid mass transfer effect. The second purification zone 12 is located on the left side of the inner cavity of the flue gas purification device 8, with its bottom connected to the downstream side of the flue gas flow channel. A catalytic reactor 13 is installed within the second purification zone 12, and the shell of the catalytic reactor 13 is sealed to the flue gas outlet of the second purification zone 12. The catalytic reactor 13 is preferably a selective catalytic reduction reactor, filled with a denitrification catalyst for catalytically reducing nitrogen oxides in the flue gas to nitrogen and water.

[0024] The static mixer 11 includes an array of static mixing plates 19, on which several staggered static mixing blades 20 are inclinedly arranged. When flue gas carrying ammonia droplets flows upward through the static mixer 11, the flue gas continuously changes its flow direction under the guiding action of the static mixing blades 20, generating strong turbulence and swirl, which fully mixes the flue gas with the ammonia droplets and improves the purification efficiency.

[0025] The movable partition 14 is located between the first purification zone 9 and the second purification zone 12, and can be raised and lowered between the upper and lower positions. A power unit 22 is mounted on the top of the flue gas purification device 8, and the power unit 22 is connected to the movable partition 14 and drives its raising and lowering. The power unit 22 is preferably an electric push rod, and a limit switch is provided on one side of the electric push rod to achieve precise positioning of the movable partition 14 between the upper and lower positions.

[0026] When the movable baffle 14 is in the lower position, the bottom of the first purification zone 9 and the top of the second purification zone 12 are separated but connected. Flue gas enters the first purification zone 9 from the bottom, flows upwards through the first ammonia spray pipe 10 and the static mixer 11, and after being sprayed and absorbed to remove acidic gases and dust, it passes over the movable baffle 14 from the top of the first purification zone 9 and enters the top of the second purification zone 12. It then flows downwards through the catalytic reactor 13 for catalytic reduction and denitrification, and finally exits from the flue gas outlet at the bottom of the second purification zone 12. This is a deep purification mode, suitable for high pollution loads or conditions with strict emission standards.

[0027] When the movable baffle 14 is in the upper position, the bottoms of the first purification zone 9 and the second purification zone 12 are directly connected. After entering the first purification zone 9 from the bottom, the flue gas bypasses the spray and mixing areas and flows directly from the bottom of the first purification zone 9 into the bottom of the second purification zone 12. It then flows upwards through the catalytic reactor 13 for catalytic reduction and finally exits from the flue gas outlet of the second purification zone 12. This is an energy-saving purification mode suitable for low pollution loads or conditions sensitive to flue gas moisture content, avoiding spray liquid consumption and catalyst activity reduction due to moisture contact.

[0028] By switching the movable partition 14 up and down, the flue gas purification device 8 can flexibly select the deep purification mode or the energy-saving purification mode according to the actual operating conditions of the hot blast stove, thus achieving an optimal balance between purification efficiency and operating costs.

[0029] In this embodiment, to increase heat exchange efficiency, the heat exchange tubes 3 in each stage of the heat exchange assembly adopt a differentiated tube diameter design: the heat exchange tubes 3 in the multi-stage heat exchange assembly include at least two different tube diameter specifications. Along the flue gas flow direction, the tube diameter of the heat exchange tube 3 in the previous stage heat exchange assembly is not smaller than the tube diameter of the heat exchange tube 3 in the next stage heat exchange assembly. For example, three or more stages of heat exchange assembly can be set up, with the first stage using large-diameter heat exchange tubes 3, the second stage using medium-diameter heat exchange tubes 3, and the third stage and above using small-diameter heat exchange tubes 3. In practical applications, the tube diameter of each stage can be calculated and determined based on parameters such as the burner 2 power, flue gas temperature, flue gas flow rate, and target hot air temperature.

[0030] An ammonia water supply device 17 is provided on one side of the furnace body 1, and its output end is connected to a first ammonia water spray pipe 10 and a second ammonia water spray pipe 18. The first ammonia water spray pipe 10 is located within the first purification zone 9. The second ammonia water spray pipe 18 is located on the shell of the burner 2, and its spray end extends into the inner cavity of the burner 2 for spraying ammonia water into the inner cavity of the burner 2. The ammonia water sprayed into the inner cavity of the burner 2 undergoes a selective non-catalytic reduction reaction with nitrogen oxides in the flue gas under high temperature conditions, reducing some of the nitrogen oxides to nitrogen and water, thereby achieving in-furnace denitrification and synergistic removal of multiple pollutants.

[0031] The following describes the overall working process of the hot air furnace of the grain dryer in this embodiment.

[0032] Flue gas side working process: Burner 2 burns fuel to generate high-temperature flue gas. Under the suction of the top induced draft fan 4, the high-temperature flue gas is discharged from the high-temperature flue gas discharge port of burner 2. It first enters the upper flue gas chamber 15 of the first-stage heat exchange component, flows downward through the inner cavity of each heat exchange tube 3 of the first-stage heat exchange component, and transfers some heat to the air in the air heating channel through the tube wall. After the flue gas temperature is reduced, it enters the lower flue gas chamber 16 of the first-stage heat exchange component. Then the flue gas enters the lower flue gas chamber 16 of the second-stage heat exchange component, flows upward through the inner cavity of each heat exchange tube 3 of the second-stage heat exchange component, and continues to transfer heat to the air in the air heating channel. After the temperature is further reduced, it enters the upper flue gas chamber 15 of the third-stage heat exchange component. And so on, the flue gas flows through each stage of the heat exchange component, releases heat step by step, and is discharged from the upper flue gas chamber 15 of the last stage heat exchange component through the top induced draft fan 4, and enters the flue gas purification device 8.

[0033] After the flue gas enters the flue gas purification device 8, the purification mode is selected according to the actual working conditions: When deep purification is required, the operator lowers the movable baffle 14 to the lower position through the power device 22. The flue gas enters from the bottom of the first purification zone 9, flows upward through the first ammonia water spray pipe 10 and the static mixer 11, and removes acidic gases and dust particles through spray absorption. Then, it turns from the top of the first purification zone 9 into the second purification zone 12, flows downward through the catalytic reactor 13 for catalytic reduction and denitrification, and is discharged after reaching the purification standard. When the pollutant concentration is low or to protect the catalyst from moisture, the movable baffle 14 is raised to the upper position. After the flue gas enters from the bottom of the first purification zone 9, it does not pass through the spray and mixing areas, but directly enters the second purification zone 12 from the bottom, flows upward through the catalytic reactor 13 for treatment, and is discharged.

[0034] Air-side working process: External cold air enters the furnace body 1 through the first air inlet 5 and the second air inlet 6. The cold air entering through the first air inlet 5 flows laterally through the outer walls of the heat exchange tubes 3 in each stage of the heat exchange components within the air heating channel. It absorbs heat from the high-temperature flue gas inside the heat exchange tubes 3 through inter-wall heat exchange, and its temperature gradually increases, forming the first stream of hot air. The cold air entering through the second air inlet 6 flows out evenly from the through holes in the furnace bottom plate 21, flows upward around the outer periphery of the burner 2 shell, absorbs radiant and convective heat from the burner 2 shell, and its temperature increases, forming the second stream of hot air. The first and second streams of hot air converge at the top of the furnace body 1, mix to the target temperature, and then flow out through the hot air outlet 7. Under the negative pressure of the dryer-side induced draft device, they enter the dryer for grain drying.

[0035] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A hot air furnace for a grain dryer, comprising a furnace body (1), wherein burners (2) and heat exchange tubes (3) are arranged laterally within the inner cavity of the furnace body (1), characterized in that, The flue gas outlet of the burner (2) is connected to the heat exchange tube (3), and the outlet end of the heat exchange tube (3) is connected to the top induced draft fan (4). The top induced draft fan (4) guides the flue gas flow through each heat exchange tube (3) and then discharges it. The furnace body (1) is provided with a first air inlet (5) on the side away from the burner (2), and a second air inlet (6) is provided on the furnace body (1) at the bottom of the burner (2). An air heating channel is formed between the outer wall of the heat exchange tube (3) and the internal space of the furnace body (1). A hot air outlet (7) is provided at the top of the furnace body (1). The air in the air heating channel flows out under negative pressure at the hot air outlet (7). The flue gas duct is also equipped with a flue gas purification device (8), including: The first purification zone (9) is located on one side of the inner cavity of the flue gas purification device (8), and its bottom is connected to the upstream side of the flue gas flow channel. The first purification zone (9) is provided with a first ammonia water spray pipe (10) and a static mixer (11) arranged along the airflow direction. The second purification zone (12) is located on the other side of the inner cavity of the flue gas purification device (8), and its bottom is connected to the downstream side of the flue gas flow channel. A catalytic reactor (13) is provided in the second purification zone (12), and the shell of the catalytic reactor (13) is sealed to the flue gas outlet of the second purification zone (12). A movable partition (14) is disposed between the first purification zone (9) and the second purification zone (12). The movable partition (14) can switch between an upper position and a lower position. When the movable partition (14) is in the upper position, the bottoms of the first purification zone (9) and the second purification zone (12) are directly connected. When the movable partition (14) is in the lower position, the bottoms of the first purification zone (9) and the second purification zone (12) are separated and the tops are connected.

2. The hot air furnace of a grain dryer according to claim 1, characterized in that, The heat exchange tube (3) is arranged as a multi-stage heat exchange assembly. Each heat exchange assembly is provided with an upper flue gas chamber (15) and a lower flue gas chamber (16). The upper flue gas chamber (15) or lower flue gas chamber (16) of adjacent heat exchange assemblies are connected to form a series flue gas flow channel. The top induced draft fan (4) is connected to the upper flue gas chamber (15) of the last stage heat exchange assembly.

3. The hot air furnace of a grain dryer according to claim 2, characterized in that, The flue gas purification device (8) is placed on the top of the furnace body (1), and its first purification zone (9) and second purification zone (12) are respectively connected to the upper flue gas chamber (15) of the two adjacent heat exchange components.

4. The hot air furnace of a grain dryer according to claim 2, characterized in that, The heat exchange tubes (3) in the multi-stage heat exchange assembly include at least two different diameter specifications, and the diameter of the heat exchange tubes (3) in the upstream heat exchange assembly is not less than the diameter of the heat exchange tubes (3) in the downstream heat exchange assembly.

5. The hot air furnace of a grain dryer according to claim 1, characterized in that, An ammonia supply device (17) is provided on one side of the furnace body (1). The delivery end of the ammonia supply device (17) is connected to a first ammonia spray pipe (10) and a second ammonia spray pipe (18). The second ammonia spray pipe (18) is connected to the burner (2) shell and sprays towards its inner cavity.

6. The hot air furnace of a grain dryer according to claim 1, characterized in that, The static mixer (11) includes an array of static mixing fixing plates (19), on which a plurality of staggered static mixing blades (20) are inclinedly arranged.

7. The hot air furnace of a grain dryer according to claim 1, characterized in that, The second air inlet (6) is opened on the bottom plate (21) of the furnace and includes several through holes evenly spaced in the circumferential direction. The second air inlet (6) is arranged around the outer periphery of the burner (2) shell.

8. The hot air furnace of a grain dryer according to claim 1, characterized in that, The top of the flue gas purification device (8) is equipped with a power unit (22), which is connected to the movable partition (14) and drives it to rise and fall.

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